Organic light emitting element with resonant structure

ABSTRACT

An organic light emitting element having a metal thin film on an upper surface of an organic thin film, is produced by mechanically cutting the metal thin film, using the cut metal thin film as a mask, and applying dry etching processing to the whole of the organic thin film and to a part of each of the thin films on the upper and lower surfaces of the organic thin film.

BACKGROUND INVENTION

The present invention relates to an organic light emitting element,especially to an organic light emitting element of the type used inoptical instruments having an optical device, such as a light source,for display, an optical circuit, an optical switch, an optical array, anoptical communication element, a head for optical recording, and soforth.

A resonator structure formed by sandwiching an organic light emittingthin film between two plane reflectors is used in a conventionalelectro-luminescent element, as disclosed, for example, in a papertitled "Investigations on Multicolor Display by Organic LuminescentDevices with Optical Microcavity Structure", by Nakayama, Tsunoda andNagae, The Transaction of the Institute of Electronics, Information andCommunication Engineers of Japan, J77-CII, pp 437-443 (1994).

In an organic electro-luminescent element using a conventionalmicro-resonator structure, no means is provided for confining lightproceeding in a direction parallel to the organic electro-luminescentfilm, and so light proceeding in that direction is lost. This problemoccurs similarly in an ordinary type electro-luminescent element inwhich a micro-resonator structure is not used.

In the following, an explanation will be given as to why lightproceeding in a direction parallel to an organic electro-luminescentfilm attenuates and is lost. At first, with reference to FIG. 11, amethod of producing an organic light emitting element will be explained.Reference mark A indicates a substrate of the organic light emittingelement, and a film B is formed by a vapor deposition method using anorganic material. Regions to be masked from vapor deposition of theorganic material vaporized in a vapor deposition source D are masked bya metal mask C.

In the vapor deposition apparatus shown in FIG. 11, a very narrow gap,which can be observed only by an optical microscope, exists between anedge of the mask C and the surface of the growing organic thin film. Thegap is generated by unevenness of the substrate A, a bend in the mask C,a roundish shape of the edge part of the mask C, etc. Assuming that thewidth of the gap is 0.1 mm (=100 μm), and the visual angle of the vapordeposition source D viewed from the edge part is 2 deg., the variationin the growing length of the thin film is 3.5 μm (=100 μm×tan(2 deg.)).That is, the thickness of the thin film changes from 100% to 0% in theinterval of 3.5 μm.

Usually, since the thickness of an organic thin film, such as one usedfor an organic light emitting element, is about 0.1 μm, the ratio of thethickness of the organic thin film to the thickness changing interval is1/35. Therefore, if the thin film is formed by a vapor deposition methodusing a mask, the angle of the edge part in the thin film is 1.6 deg.(=arc tan (1/35)) as shown in FIG. 12. Thus, light which enters theabove-mentioned edge part of the thin film is repeatedly reflected bythe inner faces of the thin film as it proceeds, as shown in FIG. 12,and attenuates until finally it is extinguished.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide an organic lightemitting element wherein light proceeding in parallel to an organic thinfilm, which ordinarily would be lost, can be effectively utilized.

A second object of the present invention is to provide an organic lightemitting element wherein a classical or quantum effect (correction oflight emission enhancement due to the transition probability mechanism)brought about by the confinement or resonance of light is applicable.

A third object of the present invention is to provide a method ofproducing a highly pure organic thin film used in an organic lightemitting element. To attain the above objects, the present invention hasthe following features.

A first feature of the present invention is to provide an organic lightemitting element, including an organic thin film formed on a substrate,wherein a peripheral side surface of the organic thin film has asectional shape such that emitted light is reflected by the sidesurface.

A second feature of the present invention is to provide an organic lightemitting element, including an organic thin film formed on a substrate,wherein the difference between a refraction index of the organic thinfilm and that of an ambient substance outside the organic thin film isset such that emitted light is confined in the organic thin film by aperipheral side surface of the organic thin film.

A third feature of the present invention is to provide an organic lightemitting element, including an organic thin film formed on a substrate,wherein a peripheral side surface of the organic thin film stands, in arange of 50%-90% of the thickness of the organic thin film,perpendicular to the substrate.

A fourth feature of the present invention is to provide an organic lightemitting element, comprising a multilayer element formed of atranslucent reflector film, a transparent electrode, a light emittinglayer and a metal electrode, wherein an optical resonator is positionedbetween the translucent reflector film and the metal electrode on thelight emitting layer in a direction perpendicular to the organic lightemitting layer, and a plurality of layer parts, each of the layer partsincluding the light emitting layer and the metal electrode, areseparately arranged in a plane parallel to the substrate, respectively,the distance between each corresponding layer in neighboring layer partsbeing larger than 1/4 of a wavelength of light emitted in the lightemitting element.

A fifth feature of the present invention is to provide a method ofproducing an organic light emitting element including an organic thinfilm, the method comprising the steps of forming a metal thin film onthe organic thin film, forming a mask of a desired pattern by physicallyor mechanically removing parts of the metal thin film, and applying dryetching processing to the organic thin film with the mask.

A sixth feature of the present invention is to provide an organic lightemitting element having a resonator structure arranged in a directionperpendicular to a substrate of the light emitting element, theresonator structure being formed by sandwiching an organic thin film inthe light emitting element between two reflectors, the organic lightemitting element comprising one of a line layer structure and a dotlayer structure in the organic thin film and a part of the thin filmsformed on the top face and bottom face of the organic thin film, inwhich line layers or dot layers are periodically arranged in parallel tothe organic thin film, wherein each two line layers neighboring eachother or each two dot layers neighboring each other have a differentmaterial composition or material structure, and the period of thearrangement, which is represented by an optical length expressed as ageometrical length×a refraction index in material of each layer, issubstantially 1/4 of a wavelength of light emitted in the organic thinfilm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an organic electro-luminescence (lightemitting) element having a micro-resonator structure, of which aperipheral side face is processed.

FIG. 2 is a diagram showing the compositions of examples of materialused in the organic thin film shown in FIG. 1.

FIG. 3 is a graph showing light transmission characteristics of atranslucent reflection layer used in the organic electro-luminescenceelement.

FIG. 4 is an conceptual diagram for showing a cutting process forproducing the organic electro-luminescence element according to thepresent invention.

FIG. 5 is a scanning tunneling microscope (STM) image of a sectionalface of an organic electro-luminescence element which was cut by ancutting process.

FIG. 6 is a scanning electron microscope (SEM) image of a sectional faceof an organic electro-luminescence element which was etched by anetching process.

FIGS. 7A to 7C are sectional views of light emitting elements whosedepths, formed by the etching process, are different from each other,which elements are etched in their depth to the bottom surface of theorganic thin film, to the bottom surface of an ITO film, and to thebottom surface of a translucent reflection film, respectively.

FIG. 8 is a sectional view of an element in which, by forming aninsulation film on an organic light emitting element, further coveringover the insulation film with a metal reflection film, the effect oflight reflection by a side face is further improved.

FIGS. 9A and 9B shows sectional views of organic light emitting elementshaving a three-dimensional light confinement structure, and atwo-dimensional light confinement structure, respectively.

FIGS. 10A, 10B and 10C are diagrammatic views which show features of anoptical device representing an embodiment according to the presentinvention, and are represented as a sectional view of the device, acomposition of matrix type electrodes of the device, and a partialperspective view of the optical device, respectively.

FIG. 11 is a diagram conceptually showing an arrangement for forming anorganic thin film.

FIG. 12 is an enlarged sectional view of the peripheral side part of anorganic thin film.

FIG. 13 is a diagrammatic perspective view for showing a composition ofan organic light emitting element having a micro-resonator structurewherein a light emitting layer has a structure of a periodicallyarranged line layer pattern.

FIG. 14 is a diagram for explaining a method of producing a periodicallyarranged line or dot layer minute pattern.

FIG. 15 is a diagrammatic perspective view for showing a composition ofan organic light emitting element having a micro-resonator structurewherein a light emitting layer has a structure of a periodicallyarranged dot layer pattern.

FIG. 16 is a diagrammatic perspective view for showing a composition ofan organic light emitting element having a micro-resonator structurewherein a light emitting layer has a structure of a periodicallyarranged layer pattern in the direction perpendicular to the substrate,in addition to the direction parallel to the substrate.

FIG. 17 is a graph showing the relation between a luminescent intensitypeak ratio of emitted light and an optical length of a resonator or aperiodical line type layer (optical length of a resonator or aperiodical line type layer/a wavelength of emitted light).

FIG. 18 is a diagrammatic perspective view for showing a composition ofan organic electro-luminescence element having a micro-resonatorstructure wherein a structure of a periodically arranged line layerpattern is formed at a light emitting layer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Details of various embodiments according to the present invention willbe explained with reference to the drawings.

FIG. 1 shows an organic light emitting element having a micro-resonatorstructure, representing an embodiment according to the presentinvention. Shaping a peripheral side face of the organic light emittingelement, by removing a part thereof outside an area to be formed as alight emitting element is carried out to an intermediate position in thethickness of a transparent electrode film 103. In FIG. 1, a laminatedtwo layer type p/n EL (Electro-Luminescence) element composed of a lightemitting layer and a hole transport layer is shown. However, a one layertype or a more than two layer type organic light emitting element, inwhich functions of the above-mentioned two organic layers are integratedinto one organic layer, or are shared by more than two organic layers,has been reported, and those types of organic light emitting elementsalso can be used for the present invention.

In FIG. 1, a translucent film 102 mace of titanium oxide or silicondioxide is formed on a glass substrate 101, and a transparent electrode103, a hole transport layer 104, a light emitting layer 105 and a metalback surface electrode 106 are layered in turn on the translucent film102. As the above material, the material described in theabove-mentioned paper presented in the transaction of the institute ofelectronics, information and communication engineers C-II, J77-C-II, 437(1994), by the inventor of the present invention, etc., can be used, andother kinds of material having a property similar to that of the abovematerial are also applicable to the present invention.

Furthermore, a feature of the present invention is that a peripheralside face of the organic thin film is shaped such that the side facefunctions as a translucent reflector due to the difference between arefraction index of the organic thin film and that of the ambientsubstance outside the organic thin film, and light emitted in theorganic thin film is reflected into the inside of the organic thin filmby the side face. That is, the attenuation and the extinction of emittedlight is prevented by forming the above-mentioned interval in which thethickness of the organic thin film gradually changes, as small aspossible, and confining the emitted light in the organic thin film.

The light emitting layer 105 and the hole transport layer 104 are madeof, for example, aluminum chelate (ALQ) and triphenyl-diamine (TAD),respectively, and their chemical structures are shown in FIG. 2. Thetransmittance of the dielectric translucent reflection film 102, formedof a 6-layer laminated film composed of titanium oxide layers andsilicon dioxide layers is indicated in FIG. 3. In the region of morethan 400 nm wavelength, light which is not transmitted in thetranslucent reflection film 102 is almost entirely reflected by thetranslucent reflection film 102.

The organic light emitting element according to the present invention isproduced by a cutting process and a dry etching process. In the cuttingprocess, a sharp edge of a cutting device, made of glass, etc., isoperated at a surface of a formed metal back surface electrode 106 in anorganic light emitting element. The cutting process is typicallyillustrated in FIG. 4. An electron microscope sectional image of thelight emitting element for which the cutting process is performed isshown in FIG. 5. Moreover, an electron microscope sectional image of thelight emitting element for which the dry etching process is furtherperformed is shown in FIG. 6. The etching conditions are indicated inTable 1. As shown in FIG. 5 and FIG. 6, a part outside the part designedto be left remaining, of the organic thin film, was removed by theetching process, and a peripheral side face of the remaining organicthin film part was finely shaped.

                  TABLE 1                                                         ______________________________________                                        Gas               CF.sub.1 (10%) + O.sub.2 (90%)                              ______________________________________                                        Pressure          2         Pa                                                RF power          200       W                                                 ______________________________________                                    

In FIG. 5 and FIG. 6, the label QUARTZ indicates the glass substrate101, the symbol ITO indicates the transparent electrode 103, the symbolTAD indicate the hole transport layer 104, the symbol ALQ indicates thelight emitting layer 105, and the symbol ALLELE indicates the metal backsurface electrode 106.

Furthermore, the above mentioned processes for producing an organiclight emitting element have an advantage in that an organic lightemitting element can be produced without using a chemical substance,such as a resist. To bring an organic EL element fully in effect, it isimportant to maintain the high purity of the organic thin film material.The mixing of a very small impurity deteriorates the performance of anorganic EL element in the extreme. Moreover, since the thickness of anorganic thin film is about 100 nm, and its volume is also very small,diffusion mixing of a very small impurity from substance, such as aresist, largely degrades the performance of the organic thin film. Theabove-mentioned production method, according to the present invention,can solve this problem of impurity. Furthermore, the production cost ofan organic light emitting element can be further reduced by using acutting device exclusive to a masking pattern in comparison with aproduction method using a resist.

The accuracy of a micro-cutting process depends on the accuracy ofmoving the edge of a cutter or of driving a substrate. By applying amicro-control technique of the type used to control a stage position ina STM (Scanning Tunneling Microscope) or a SEM (Scanning ElectronMicroscope), the accuracy of the micro-cutting at the micron level orless is possible.

Although it is desirable for the peripheral side face of an organic thinfilm to be ideally perpendicular to the surface of the substrate, if theperipheral side face of the organic thin film, in a range of about40%-90% of the thickness of the organic thin film, is perpendicular tothe surface of the substrate, light emitted in the organic thin film canbe sufficiently reflected by the peripheral side face, in other words,can be confined in the organic thin film.

FIGS. 7A, 7B and 7C shows sectional views of light emitting elements ofwhich the depths formed by the etching process are different from eachother. FIG. 7A shows a sectional view of a light emitting element, whichis etched in depth to the bottom surface of the layer 104, FIG. 7B showsa sectional view of a light emitting elements, which is etched in depthto the bottom surface of the ITO film 103 and FIG. 7C shows a sectionalview of a light emitting elements, which is etched in depth to thebottom surface of the translucent reflection film 102. In selecting oneof the above-mentioned three types of elements, an element which isoptimal for an object using an organic light emitting element isselected by considering the production cost and the effect of lightreflection by the side face. In order to etch an organic light elementdeeply, it is necessary to use a metal back surface electrode filmhaving a large thickness or to use a low etching speed type material asthe electrode film, or to mount a layer of low etching speed typematerial on the electrode and cut the mounted layer and the electrodefilm together.

As shown in FIG. 8, by forming an insulation film on an organic lightemitting element, and then covering over the insulation film with ametal reflection film, the effect of light reflection by the side faceis further improved.

FIG. 9A is a perspective view of organic light emitting elements havinga three-dimensional light confinement structure, and FIG. 9B is aperspective view of an organic light emitting element having atwo-dimensional light confinement structure.

FIG. 13 shows an organic thin film light emitting element having aresonator structure provided in a direction perpendicular to the thinfilm, and including a translucent reflection film composed of alaminated dielectric multilayer thin film. In FIG. 13, the structureincludes a glass substrate 401, a translucent reflection film 402 formedof 6 laminated layers composed of titanium oxide layers and silicondioxide layers, an organic light emitting thin film 403A, 403B, and ametal back surface electrode 404 made of an Al:Li alloy. The organiclight emitting thin film (403A and 403B) has a periodically arrangedline type layer structure. In FIG. 13, the structure of the organiclight emitting thin film (403A and 403B) is separately shown. The metalback surface electrode 404 is formed at the top of the organic lightemitting thin film (403A and 403B) by a vapor deposition method, afterthe light emitting thin film having a periodically arranged line layerstructure is formed. By irradiating the light emitting thin film withultra-violet light, the layer is excited, and it emits visual light.

FIG. 15 is an illustration showing the composition of a light emittingelement wherein an organic light emitting thin film has a structure of aperiodically arranged dot layer pattern. In a light emitting layerhaving a structure of a periodically arranged line layer pattern, onlylight proceeding in a direction perpendicular to each line is reflected.On the other hand, in a light emitting thin film having a structure of aperiodically arranged dot layer pattern, light proceeding in twodirections perpendicular to each other is reflected.

FIG. 16 is an illustration showing the composition of a light emittingelement wherein an organic light emitting thin film has the structure ofa periodically arranged layer pattern in a direction perpendicular tothe substrate, in addition to a direction parallel to the substrate.This structure of the organic light emitting thin film is formed byrepeatedly applying a series of processes for forming an organic thinfilm and processing a periodically arranged layer pattern in a directionperpendicular to the substrate.

In FIG. 14, a minute processing of a substance, for which light sentthrough an optical fiber is used, is typically and conceptuallyillustrated. In the minute processing, light sent through an opticalfiber is emitted from an aperture in the fiber. If the size of theaperture is as small as 1/4 of a wavelength of the light, usual lightcan not proceed out of the aperture. In this situation, light can existonly at a very small local area of a size of about 1/4 wavelength, whichis a so-called near-field, generated in the vicinity of the outside ofthe aperture. It has been reported in App. Phys. Lett. 61, p. 142 thatby moving the aperture in the fiber, a substance can be minutelyprocessed by the light at the near-field.

By forming the above-mentioned structures for confining emitted light ina light emitting thin film, a light resonator is formed in a lightemitting element, and it is possible to form a light emitting elementsuch that a classical or quantum effect (correction of light emissionenhancement due to the transition probability mechanism) due to thelight confinement or the light resonance is applied to the lightemitting element. Naturally, since the effect of light reflection by theside face becomes relatively larger as the surface area of the lightemitting element decreases, the effect of the shape in the side faceaccording to the present invention also becomes larger.

Hereupon, it is necessary to set the distance between two light emittingelements neighboring each other to more than 1/4 of a wavelength λ ofemitted light, for which the etching processes were performed for thestructures shown in FIGS. 7A-7C, FIG. 8 and FIG. 9A.

The reason why a distance of more than 1/4 of a wavelength λ isnecessary is because light leaking from a light emitting element reachesthe positions spaced from the element by 1/4 of λ, and leakage lightfrom light emitting elements neighboring each other will interfere witheach other.

It is well known that in many kinds of organic material, combiningbetween molecules is generated, or decomposition or phase changes, suchas crystallization will occur, when receiving energy, such as light,heat, etc. The above-mentioned physical or chemical changes in organicmaterial often cause the change of a refraction index. Therefore, it ispossible to embed layers having a function of a translucent reflector inan organic light emitting thin film by forming a periodically arrangedline or dot layer pattern in the organic thin film at a periodic lengthof 1/4, 3/4, 5/4 and so on, of a wavelength of emitted light, by makinguse of the change of a refraction index resulting from the physical orchemical change of the organic thin film. By those periodically formedlayers, light proceeding in a direction perpendicular to each line layeror each dot layer is reflected and confined.

The above-mentioned light confinement according to the present inventionis effective, especially for an organic light emitting element having aresonator structure formed by providing two reflector films, such as alaminated dielectric multilayer reflection film, at the top and bottomsurfaces of an organic light emitting thin film.

In both of the directions parallel and perpendicular to the substrata,the largess effect of the light confinement can be obtained, if theperiodic optical length, which is expressed as a geometrical length×arefraction index in material, of the embedded reflector layers in theorganic thin film is 1/4 of a wavelength of emitted light. Moreover, thelargest effect of the light confinement can be obtained, if the depth ofthe resonator is 1/4 or 1/2 of a wavelength. It depends on whether thetotal amount of phase shift due to light reflection by the reflectorfilms is one or a half of a wavelength, which depth of 1/4 or 1/2 of awavelength brings the largest effect. A periodic length or a depthlarger by 1/2 of a wavelength than the above-mentioned optimal periodiclength or depth can satisfy the light confinement or resonanceconditions.

There is actually an upper limit to an effective periodic length or adepth of a resonator, which is brought about by the unevenness ofsurfaces or boundary faces in the resonator end the periodicallyarranged layers in the organic light emitting thin film. That is, as theperiodic length or depth of a resonator increases, a quantum effect,such as a micro-resonator effect, decreases, and the strength of theresonance becomes weak, which is caused by the unevenness of surfaces inthe resonator. FIG. 17 is a graph showing the relation between arelative peak strength of emitted light and a relative optical length ofa resonator or a line type layer. As seen in FIG. 17. it is necessary toset the optical length or depth to less than 10 times the wavelength inorder to obtain a more than 10% effect related to the peak strength.

An organic light emitting thin film having a periodically arranged lineor dot layer structure functions as a translucent reflector and reflectslight with a definite ratio into the inside of the thin film.

FIG. 10A shows a luminescence panel using organic EL elements which havea three-dimensional light confinement structure. Each of the organic ELelements have the same composition as that of the organic light emittingelement shown in FIG. 1. Numerals 101, 101A indicate two glasssubstrates, and numeral 102 indicates a laminated 6-layer translucentreflection film made of titanium oxide and silicon dioxide. Moreover,the structure includes transparent electrodes made of indium-tin oxide(ITO), which have a thickness of 200 nm, hole transport layers 104 madeof triphenyl-diamine (TAD), which have a thickness of 50 nm, lightemitting layers 105 made of aluminum chelate (ALQ), which have athickness of 50 nm, and metal back surface electrodes 106 made ofaluminum-lithium alloy (allele), which have a thickness of 200 nm. Thetwo substrates 101 and 101A are adhered to each other with adhesive 302,and the light emitting elements are contained in a space 301 between thetwo substrates 101 and 101A. Dry nitrogen gas is enclosed in the space301.

As shown in FIG. 10B, the transparent front surface electrodes 103 andthe metal back surface electrodes 303 form a matrix type arrangement ofelectrodes by which light emitting parts are selected. Projecting parts304, which are made of soft metal, such as In, are formed on theelectrodes 303, and the transparent front surface electrodes 106 and themetal back surface electrodes 303 are pressurized and connected to eachother via the projecting parts 304. In this composition, an insulatingmember is necessary to prevent the electrodes 103 from contacting to theelectrodes 303 at places other than the luminescence pixel parts.

The number of organic light emitting elements arranged at each of theelement areas, with the electrodes 303 and the electrodes 103intersecting each other at the element areas as shown in FIG. 10B, isnot restricted to one, but more than one organic light emitting elementcan be arranged at each of the element areas. In an embodiment shown inFIG. 10C, two light emitting elements are arranged at each of theelement areas.

FIG. 18 is a sectional view of an organic light emitting elementrepresenting an embodiment according to the present invention. In theorganic light emitting element shown in FIG. 18, a laminated-layer thinfilm composed of titanium oxide layers (the thickness of each layer is54 nm) and silicon dioxide layers (the thickness of each layer is 86 nm)is used as a dielectric translucent reflection film. Moreover, in FIG.18, the chemical structure of a polyacetylene derivative is shown, whichis used for an organic light emitting layer. The refraction index of apolyacetylene film can be changed by growing the principal chain ofcarbon bonding in the polyacetylene derivative using a photoreactionprocessing. The spectrum of light emitted by the polyacetylenederivative can be changed by changing the kinds of molecules which arecombined to branches of the polyacetylene derivative. The thickness ofthe metal back surface electrode 404 is 200 nm. Moreover, numeral 405indicates a transparent electrode made of ITO and having a thickness of200 nm. By applying a voltage between the electrodes 404 and 405,electrons and holes are injected into the light emitting layer and arerecombined, to further excite the organic material of the layer. Thus,light is emitted from the excited organic material.

Although an example of an EL (electro-luminescence) element of a onelayer type element structure has been explained with reference to FIG.18, a report of a two layer type or more than 2 layer type EL element,in which the functions of the above-mentioned one layer type element areshared to two or more organic layers, has been presented, and those typeEL elements are also applicable to the present invention.

In accordance with the present invention, since light emitted in a lightemitting thin film is reflected into the inside of the layer by aperipheral side face of the shape formed according to the presentinvention at a definite ratio of the quantity of light reflected by theside face to the quantity of light reaching the side face, the lostquantity of emitted light can be reduced, and the total quantity ofeffective light output from the front surface of the light emitting thinfilm can be increased. That is, the ratio of the quantity of lightoutput from a light emitting element to the quantity of energy inputinto the light emitting element is improved. By forming theabove-mentioned structures for confining emitted light in a lightemitting film, it is possible to form an organic light emitting elementsuch that a light resonator is obtained, and a classical or quantumeffect (correction of light emission enhancement due to the transitionprobability mechanism) due to the light confinement or the lightresonance can be applied to the light emitting element.

What is claimed is:
 1. An organic light emitting element having aresonator structure in a direction perpendicular to a substrate of saidlight emitting element, said resonator structure being composed bysandwiching an organic thin film in said light emitting element betweenreflectors, said organic light emitting element comprising:one of aperiodic line layer structure and a periodic dot layer structure in saidorganic thin film and a part of thin films formed on the top face andbottom faces of the organic thin film, in which line layers or dotlayers are periodically arranged in parallel to said organic thin film,wherein each two line layers neighboring each other or each two dotlayers neighboring each other have different material compositions ormaterial structures, and a period of said layer arrangement, which isrepresented by an optical length expressed as a geometrical length×arefraction index in material of each layer, is substantially 1/4 of awavelength in each layer of light emitted in said organic thin film. 2.An organic light emitting element according to claim 1, wherein saidperiod is (1+2m)/4 of the wavelength of light in each layer, where m isan integer taking a value in a range of 1 to
 19. 3. An organic lightemitting element according to claim 2, wherein said periodic layerstructure is formed by using a near-field light.
 4. An organic lightemitting element according to claim 2, further including a translucentreflector and a transparent conductive film, composed of dielectricmultilayer films, wherein said organic thin film emits light by applyinga voltage to said organic thin film.
 5. An organic light emittingelement according to claim 2, wherein said periodic structure composesone of two-dimensional and three-dimensional resonators by making use oflight reflection due to different refraction indexes in each two layersneighboring each of other.